Identity should get the data protection provider from the environment

[GrabYourPitchforks]

Currently Identity creates its own protection provider (see

Identity/src/Microsoft.AspNet.Identity/IdentityServiceCollectionExtensions.cs

Line 105 in 0a91227

// TODO: This needs to get IDataProtectionProvider from the environment

) for token protection. This doesn't work in farms or across resets. Identity should instead get the protection provider from the services collection.